Not support async??

[khanh-bh]

I got an issue that my mobile app lags for a while when I ran scrypt(). We pass a progress callback but it is not actually asynchronous.

[woodser]

I also needed async support.

I forked scryptsy with async support here: https://github.com/cryptostorage/scryptsy.

And bitcoinjs/bip38 with async support here: https://github.com/cryptostorage/bip38.

It would be great if support for async were merged upstream.